Head coach Lindy Ruff announced the move on Saturday as the Sabres opened training camp.
Numminen retired in 2009 following a 20-year NHL career, in which he spent the final four seasons with Buffalo. The native of Finland had 117 goals and 520 assists in 1,372 career games. He holds the NHL record for most games played by a European-developed player.
He missed all but one game of the 2007-08 season after having heart surgery, before returning to play in 57 games the following season.